1 /*
2  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
3  * Copyright (C) 2006-2008 Red Hat GmbH
4  *
5  * This file is released under the GPL.
6  */
7 
8 #include "dm-exception-store.h"
9 #include "dm-snap.h"
10 
11 #include <linux/mm.h>
12 #include <linux/pagemap.h>
13 #include <linux/vmalloc.h>
14 #include <linux/slab.h>
15 #include <linux/dm-io.h>
16 
17 #define DM_MSG_PREFIX "transient snapshot"
18 
19 /*-----------------------------------------------------------------
20  * Implementation of the store for non-persistent snapshots.
21  *---------------------------------------------------------------*/
22 struct transient_c {
23 	sector_t next_free;
24 };
25 
26 static void transient_dtr(struct dm_exception_store *store)
27 {
28 	kfree(store->context);
29 }
30 
31 static int transient_read_metadata(struct dm_exception_store *store,
32 				   int (*callback)(void *callback_context,
33 						   chunk_t old, chunk_t new),
34 				   void *callback_context)
35 {
36 	return 0;
37 }
38 
39 static int transient_prepare_exception(struct dm_exception_store *store,
40 				       struct dm_snap_exception *e)
41 {
42 	struct transient_c *tc = store->context;
43 	sector_t size = get_dev_size(store->snap->cow->bdev);
44 
45 	if (size < (tc->next_free + store->snap->chunk_size))
46 		return -1;
47 
48 	e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
49 	tc->next_free += store->snap->chunk_size;
50 
51 	return 0;
52 }
53 
54 static void transient_commit_exception(struct dm_exception_store *store,
55 				       struct dm_snap_exception *e,
56 				       void (*callback) (void *, int success),
57 				       void *callback_context)
58 {
59 	/* Just succeed */
60 	callback(callback_context, 1);
61 }
62 
63 static void transient_fraction_full(struct dm_exception_store *store,
64 				    sector_t *numerator, sector_t *denominator)
65 {
66 	*numerator = ((struct transient_c *) store->context)->next_free;
67 	*denominator = get_dev_size(store->snap->cow->bdev);
68 }
69 
70 static int transient_ctr(struct dm_exception_store *store,
71 			 unsigned argc, char **argv)
72 {
73 	struct transient_c *tc;
74 
75 	tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
76 	if (!tc)
77 		return -ENOMEM;
78 
79 	tc->next_free = 0;
80 	store->context = tc;
81 
82 	return 0;
83 }
84 
85 static int transient_status(struct dm_exception_store *store,
86 			    status_type_t status, char *result,
87 			    unsigned maxlen)
88 {
89 	int sz = 0;
90 
91 	return sz;
92 }
93 
94 static struct dm_exception_store_type _transient_type = {
95 	.name = "transient",
96 	.module = THIS_MODULE,
97 	.ctr = transient_ctr,
98 	.dtr = transient_dtr,
99 	.read_metadata = transient_read_metadata,
100 	.prepare_exception = transient_prepare_exception,
101 	.commit_exception = transient_commit_exception,
102 	.fraction_full = transient_fraction_full,
103 	.status = transient_status,
104 };
105 
106 static struct dm_exception_store_type _transient_compat_type = {
107 	.name = "N",
108 	.module = THIS_MODULE,
109 	.ctr = transient_ctr,
110 	.dtr = transient_dtr,
111 	.read_metadata = transient_read_metadata,
112 	.prepare_exception = transient_prepare_exception,
113 	.commit_exception = transient_commit_exception,
114 	.fraction_full = transient_fraction_full,
115 	.status = transient_status,
116 };
117 
118 int dm_transient_snapshot_init(void)
119 {
120 	int r;
121 
122 	r = dm_exception_store_type_register(&_transient_type);
123 	if (r) {
124 		DMWARN("Unable to register transient exception store type");
125 		return r;
126 	}
127 
128 	r = dm_exception_store_type_register(&_transient_compat_type);
129 	if (r) {
130 		DMWARN("Unable to register old-style transient "
131 		       "exception store type");
132 		dm_exception_store_type_unregister(&_transient_type);
133 		return r;
134 	}
135 
136 	return r;
137 }
138 
139 void dm_transient_snapshot_exit(void)
140 {
141 	dm_exception_store_type_unregister(&_transient_type);
142 	dm_exception_store_type_unregister(&_transient_compat_type);
143 }
144